Digital Communication System and a Method of Transferring Power and Data Between Circuits of the System

1. A method of transferring power and data between a first circuit and a second circuit, whereby the second circuit comprises a processing unit having an I/O terminal and an electric energy storage element, the electric energy storage element being configured to be charged by the first circuit via the I/O terminal and configured to power the processing unit, the method comprising: establishing a wired communication link between an I/O terminal of the first circuit and the I/O terminal of the second circuit; operating the I/O terminal of the second circuit as an output terminal and the I/O terminal of the first circuit as an input terminal; transmitting data via the I/O terminal of the second circuit to the I/O terminal of the first circuit by modulating an output level of the I/O terminal of the second circuit between a high level and a low level; and determining whether the output level of the I/O terminal of the second circuit corresponds to the high level or the low level and, when the output level corresponds to the high level: operating the I/O terminal of the first circuit as an output terminal; and raising an output level of the I/O terminal of the first circuit to a level that is at least equal to the high level during at least part of a period when the output level of the I/O terminal of the second circuit corresponds to the high level, thereby charging the electric energy storage element of the second circuit during the transmitting data via the I/O terminal of the second circuit to the I/O terminal of the first circuit.

2. The method according to claim 1 , further comprising: operating the I/O terminal of the first circuit back as an input terminal when the output level corresponds to the low level.

3. The method according to claim 1 , further comprising: operating the I/O terminal of the first circuit back as an input terminal prior to the output level of the I/O terminal of the second circuit corresponding to the low level.

4. The method according to claim 1 , wherein the step of modulating the output level of the I/O terminal of the second circuit between the high level and the low level includes modulating the output level in accordance with a Manchester encoding or differential Manchester encoding.

5. The method according to claim 1 , wherein the step of operating the I/O terminal of the first circuit back as an input terminal is based on a period of a clock signal of the second circuit.

6. A digital communication system comprising a first circuit and a second circuit, the first circuit comprising: a processing unit having an I/O terminal and having a power-supply terminal connectable to a power source; the second circuit comprising: a processing unit having an I/O terminal connected or connectable to the I/O terminal of the first circuit via a communication link; an electric energy storage element configured to supply power to the processing unit, the electric energy storage element being configured to be charged via the I/O terminal, whereby the processing unit of the second circuit is configured to: operate the I/O terminal as an output terminal; transmit data by modulating an output level of the I/O terminal between a high level and a low level and whereby the processing unit of the first circuit is configured to: operate the I/O terminal as an input terminal, and, during a transmission of data by the processing unit of the second circuit: determining whether the output level of the I/O terminal of the second circuit corresponds to the high level or the low level and, when the output level corresponds to the high level: operating the I/O terminal of the first circuit as an output terminal; and raising an output level of the I/O terminal of the first circuit to a level that is at least equal to the high level during at least part of a period when the output level of the I/O terminal of the second circuit corresponds to the high level, thereby charging the electric energy storage element of the second circuit during the transmission of data via the I/O terminal of the second circuit to the I/O terminal of the first circuit.

7. The digital communication system according to claim 6 , wherein the electric energy storage element is connected to the I/O terminal via a unidirectional switch such as a diode.

8. The digital communication system according to claim 6 , wherein the electric energy storage element is a capacitor.

9. The digital communication system according to claim 6 , wherein the second circuit comprises a power supply terminal, the electric energy storage element being connected to the power supply terminal.

10. The digital communication system according to claim 6 , wherein the second circuit is incorporated in a device.

11. The digital communication system according to claim 10 , wherein the device comprises a sensor, the sensor being configured to provide a sensing signal to the processing unit.

12. The digital communication system according to claim 11 , wherein the processing unit is configured to transmit sensor data representative of the sensing signal via the I/O terminal to the first circuit.

13. The digital communication system according to claim 11 , wherein the sensor comprises an environmental sensor or an illumination sensor.

14. The digital communication system according to claim 6 , wherein the processing unit of the second circuit is configured to modulating the output level of the I/O terminal of the second circuit between the high level and the low level in accordance with a Manchester encoding or differential Manchester encoding.

15. The digital communication system according to claim 6 , wherein the processing unit of the first circuit is configured to: operating the I/O terminal of the first circuit back as an input terminal when the output level corresponds to the low level.

16. The digital communication system according to claim 15 , wherein the processing unit of the first circuit is configured to operating the I/O terminal of the first circuit back as an input terminal based on a period of a clock signal of the second circuit.

17. A circuit for use in a digital communication system enabling communication between the circuit and a further circuit, the circuit comprising: a processing unit having an I/O terminal connectable to an I/O terminal of the further circuit, and having a power-supply terminal connectable to a power source; whereby the processing unit of the circuit is configured to: operate the I/O terminal as an input terminal, and, during a transmission of data by the further circuit: determining whether the output level of the I/O terminal of the further circuit corresponds to a high level or a low level and, when the output level corresponds to the high level: operating the I/O terminal of the circuit as an output terminal; and raising an output level of the I/O terminal of the circuit to a level that is at least equal to the high level during at least part of a period when the output level of the I/O terminal of the further circuit corresponds to the high level during the transmission of data via the I/O terminal of the further circuit to the I/O terminal of the circuit.